1. Field of the Art
This invention relates to an apparatus for giving a workpiece (hereinafter referred to simply as "work" for brevity) on a work table progressive abrasion treatments with blasts of a mixture of fine powder and high-pressure gas or air, for example, in a surface etching process or in a grinding operation or in a boring or piercing operation.
More particularly, the invention concerns a novel apparatus for abrasion treatments with blasts of fine powder mixture, which is capable of treating a number of works concurrently and progressively with blasts of powder and compressed air mixture in a predetermined sequence to shorten the so-called tact time.
2. Description of the Prior Art
The powder blasting machines, which are arranged to blast mixture powder of metal and inorganic material or the like against a work with aid of a high pressure gas, have been known and used in the art as means for grinding or boring or perforating a workpiece, for example, as means for forming fine blind holes or through holes in substrates of electronic devices.
The machines of this sort are basically constituted by a work table adapted to hold a work thereon, a transfer means for loading and ejecting the work onto and from the work table, a nozzle for blasting a powder mixture toward the work, a powder feed means for supplying high-pressure compressed air and powder mixture to the nozzle, a powder recovery means for collecting spent powder mixture which has been used for the powder blasting treatment, and an air compressor serving as a compressed air source. In this instance, the work is masked except for those areas where blind or through holes are to be formed, so that, as the powder mixture is blasted- against the work, blind or through holes are formed in predetermined positions on the work.
For example, as mentioned above, the holes to be formed on a substrate include two types of holes, i.e., a through hole which is open on the opposite sides of the substrate and a blind hole which is open only on one side of the substrate. In this regard, it is often the case that, in addition to through holes, a variety of blind holes of different depths need to be formed on each substrate.
In order to form a variety of holes on a substrate by the use of a single blast nozzle, it becomes necessary to blast the mixture powder against predetermined areas of the work for different time periods depending upon the type of holes to be formed, namely, over a relatively short time period for a shallow blind hole, over a prolonged time period for a deeper blind hole and over a further prolonged time period for a through hole, taking an objectionably long time in forming various holes into each substrate.
This problem is accompanied by another problem that, in the production line of substrates, the overly time consumption in the boring or perforating stage causes stagnation of works in other stages of the production line, resulting in a lengthy tact time throughout the line.